Pilot operated hydraulic valve actuator

Abstract

A housing has a pilot bore with an electrically controlled pilot valve therein, an intermediate bore with an intermediate valve therein, and an engine bore with a main valve therein, each valve being reciprocable between first and second stable positions. When said pilot valve is switched to its first stable position, high pressure hydraulic fluid drives said intermediate valve to its first stable position and releases said engine valve from its second stable position, whereupon a double acting spring drives the engine valve toward its first stable position. High pressure hydraulic fluid completes this movement then holds the main valve in its first stable position against the force of the double acting spring. Switching the pilot valve to its second stable position effects movement of the other valves back to their second stable positions.

What is claimed is: 
     
       1. An electrically controlled engine valve actuator assembly comprising a valve actuator housing having a pilot bore, an intermediate bore, and a main bore therein,   high pressure galley means connected to said pilot bore for supplying hydraulic fluid from a high pressure source,   low pressure galley means connected to said pilot bore for supplying hydraulic fluid from a low pressure source,   an electrically controlled bistable pilot valve reciprocable in said pilot bore between first and second stable positions,   a hydraulically powered bistable intermediate valve reciprocable in said bore between first and second stable positions responsive to reciprocation of said pilot valve between respective first and second stable positions,   an engine valve reciprocable in said main bore between first and second stable positions and having a working piston with opposed first and second working surfaces for receiving hydraulic fluid pressure for moving said engine valve toward respective first and second stable positions,   double acting spring means which, when said engine valve is in said first stable position, urges said engine valve toward said second stable position, and, when said engine valve is in said second stable position, urges said engine valve toward said first stable position, and   hydraulic connecting means including said pilot valve and said intermediate valve for connecting said high pressure galley means to said first working surface and said low pressure galley means to said second working surface when said pilot valve and said intermediate valve are in their first stable positions, and for connecting said high pressure galley means to said second working surface and said low pressure galley means to said first working surface when said pilot valve and said intermediate valve are in their second stable positions.   
     
     
       2. A valve actuator assembly as in claim 1 wherein said intermediate valve has opposed first and second working surfaces for receiving hydraulic fluid pressure for moving said intermediate valve toward respective first and second stable positions when said pilot valve is in respective first and second stable positions.   
     
     
       3. A valve assembly as in claim 2 wherein said hydraulic connecting means further comprises a first working galley connecting said pilot bore to said first working surface of said intermediate valve and a second working galley connecting said pilot bore to said second working surface of said intermediate valve, and   said pilot valve comprises means connecting said high pressure galley means to said first working galley and said low pressure galley means to said second working galley when said pilot valve is in said first stable position, and means connecting said high pressure galley means to said second working galley and said low pressure galley means to said first working galley when said pilot valve is in said second stable position.   
     
     
       4. A valve actuator assembly as in claim 3 wherein said low pressure galley means comprises first and second low pressure galleys and said high pressure galley means comprises a high pressure galley connected to said pilot bore between said first and second low pressure galleys, said pilot valve being a spool valve comprising a pair of pistons closely received in said pilot bore and a constriction defining an annular space between said high pressure galley and said first working galley while one of said low pressure galleys communicates with said second working galley when said pilot valve is in said first stable position, said space communicating between said high pressure galley and said second working galley while the other low pressure galley communicates with said first working galley when said pilot valve is in said second stable position. 
     
     
       5. A valve actuator assembly as in claim 2 wherein said hydraulic connecting means further comprises third galley means connecting said high pressure source to said main bore,   said engine valve comprising a piston bearing said first and second working surfaces, said piston traversing said third galley as said main valve reciprocates between said first and second stable positions, thereby exposing said first working surface to high pressure when said main valve is in said first stable position and exposing said second working surface to said high pressure when said engine valve is in said second stable position.   
     
     
       6. A valve actuator assembly as in claim 1 wherein said engine valve is held in one of said stable positions against the force of said double acting spring means by high pressure hydraulic fluid. 
     
     
       7. A valve actuator assembly as in claim 1 wherein movement of said pilot valve from its first stable position to its second stable position releases high pressure hydraulic fluid from said first working surface of said working piston so that said double acting spring propels said engine valve toward said second stable position, and wherein movement of said pilot valve from its second stable position to its first stable position releases high pressure fluid from said second working surface of said piston so that said double acting spring propels said engine valve toward said first stable position. 
     
     
       8. A valve actuator assembly as in claim 1 further comprising transfer port means for transferring hydraulic fluid from said first working surface of said working piston to said second working surface of said working piston when said engine valve is intermediate its first and second stable positions. 
     
     
       9. A valve actuator assembly as in claim 1 further comprising an initializer bore in said housing,   an initializer valve reciprocable in said initializer bore between first and second stable positions, siad initializer valve having a constriction thereon which permits fluid communication between one of said high and low pressure galleys and one of said first and second working surfaces of said working piston when said initializer valve is in its first stable position.   
     
     
       10. A valve actuator as in claim 9 wherein, when said initializer valve is in its second stable position and said engine valve is intermediate its first and second stable positions, said constriction permits fluid communication between said first and second working surfaces of said working piston. 
     
     
       11. Valve actuator assembly as in claim 1 wherein said pilot bore, said intermediate bore, and said main bore are parallel. 
     
     
       12. Valve actuator assembly as in claim 1 wherein said main bore comprises a working chamber in which said working piston reciprocates, said double acting spring means being remote from said working chamber.